US2823282A - Electromagnetic relays - Google Patents

Description

Feb 11, 1958 F. E. ROMMEL ET AL 2,823,232

ELECTROMAGNETIC RELAYS Filed March 4, 1955 2 Sheets-Sheet l Inventors W 8, W

W a M Attorney 1958 F. E. ROMMEL ET AL 2,

ELECTROMAGNETIC RELAYS 2 Sheets-Sheet 2 Filed March 4, 1955 ELECTROMAGNETIC RELAYS Frederick Emil Rommel and Malcolm Simons, London,

England, assiguors to Telephone'Manufacturing' Company Limited, London, England, a British company Application March 4, 1955, Serial No. 492,155 Claims priority, application Great Britain March 5, 1954 11 Claims. (Cl. 200-93) This invention relates to polarised electromagnetic relays, and may be applied with particular advantage to relays of small dimensions in which the spacing between the co-operating contact members and the travel of the moving contact or contacts betweentheir closed and open positions are very small and, in fact, in practice often have to be of the order of a few thousandths' of an inch. One form of such so-called miniature relays is set forth in" British patent specification No. 619,546.

Hitherto in the manufacture of such'miniature relays, a relatively large number of component parts have had to be manufactured separately to very fine limits and then assembled. The manufacture and assembly of such parts a and the adjustment and testing of intricate relays formed 7 from them is a lengthy and expensive process requiring a high degree of human skill and careful attention. The various component parts are formed from different materials selected for their various mechanicaland electrical properties. As is known,-difliculties are usually experienced inselecting materials which satisfy both electrical and mechanical requirements at thesame time and, in particular, in selecting a group of materials having-the required properties and all of whichmay be worked to the same fine limits.

In the construction of any instrument. or apparatus, it is desirable that the numbers bothof the component parts and of the types of such parts shall be kept to a minimum. In the construction of miniature relays, it has hitherto been customary for the armature to be employed as a contact-carrying member moving its contact or contacts from one position into its other position, and thereby breaking contact or making contact or changing over contacts, and in these cases it has been usual to carry the current of the armature contact or contacts through the armature itself, and there has always been a difliculty of ensuring a constant relative location between a moving contact'and a co-op'erating fixed contact under all normal conditions of operation.

The present invention is concerned with dealing with the above problems and, as far as possible, avoiding the drawbacks mentioned. Thus, according to the present invention, in manufacturing an electromagnetic relay, the parts are arranged so that they are assembled into two separate or distinct structures, one of which includes the complete driving mechanism in operating condition, and the other contains the complete contact structure including both memorable and stationary contacts, whereupon the two separate structures are joined together to form the finished relay. The contact structure is complete in itself in controlling the circuits actuated by the relay in the sense'that the armature takes no part in the actual conduction ofthe current and is only a mechanical actuator for the moving contacts. The moving contact or each of them is arranged to be restricted in its return or backward'rnovement by a buffer or back stop surface so that its position when not actuated isdetermined with precision. B'y this means, the contacts can beset up with zszazaa Patented Feb. 11., 1 953 the necessary adjustment, and the driving member which is usually the armature-of the relay, and also the contact structure can also be set up and adjusted independently of one another without any interaction of parts of the one structure with the parts of the other structure, and without the adjustment of the one structure affecting that of the other, so that the complete method of manufacture is considerably simplified.

The invention further makes it possible that only one material is required for the component parts of the contact structure which are required to be insulating, and also only one other material is required for all components in that structure which are required to be conductive. As a result of this, all the parts of one material naturally have the same mechanical and electrical properties.

Furthermore,- only two forms of insulating parts and two forms of contact members are really essential in the contact structure. As a matter of fact, in the case of a single change-over action, only two each of the insulating components'and two'conductive components are required for the complete structure and, in the case of a double changeover action, only two of the insulating members and four of the conductive members are required, so reducing the number of different manufacturing components to a minimum.

Yet again, theinvention enables the moving contacts of the contact structure to be mounted mechanically and electrically independently of the relay armature, and also enables a constant relative position to be maintained between the fixed and moving contacts under all normal conditions, so that stringent conditions connected with the positioning of the armature can be relaxed as well as the manufacturing requirements.

The use of the relay armature actually to carry one or more contacts and, in particular, to carry the current to the contact or contacts, introduces a difiiculty of ensuring the high order of insulation resistance for the current-carrying members required by present day electronic equipment. Both owing to the location of the armature contacts and to their larger size in comparison with the static contacts, hitherto it has been seldom possible to obtain equal values of insulation resistance for both the moving and the static contacts, even although special efforts have been made to obtain that result. The forms of contact structure according to the present invention, however, enable an equal order of insulation resistance to be obtained for both the static and moving contacts, with the result that the design and manufacturing requirements of the armature structure are facilitated to a considerable degree.

As mentioned above, one of the main disadvantages of the use of the armature for carrying one or more contacts is the difiiculty of ensuring a constant relationship between the positions of the moving and static contacts and, in fact, in the manufacture of such relays, a special method of testing and adjusting the armature is required in order to ensure a correct initial'relationship between the positions of the respective contacts. Another factor which had to be taken into consideration when the armature was used to conduct current to the contacts,

' material.

the armature.

is finally assembled, which avoids a further adjustment of their component parts and, therefore, further relieves the manufacturing requirements. A completely stable linkage may be provided between the armature and the moving contacts and this linkage provides a very high order of insulation resistance, thereby considerably simplifying the design of the armature and the mode of its suspension.

The contact arrangements of a polarised relay normally may take one of six forms, that is to say, they may provide for single or double change-over action and, in either case, the relay may be one-side-stable, both-side-stable or centre-stable. Then circuitarrangements are provided to adapt individual change-over actions to single make or break actions. Hitherto, in order to provide for these six arrangements, six different relay structures have been required in which as many as possible common parts have been used but in which still numerous components have to be peculiar to each type of relay. The present invention, however, makes it possible to provide a contact structure for use in conjunction with asuitable driving mechanism with any or all of the six contact arrangements without discrimination. In addition, the invention makes it possible to produce a construction by which a centre-stable or a one-side-stable relay of either single or double contact action is produced merely by altering the relationship of the contact structure to the driving structure, and this avoids the necessity for certain special component parts and adjustment, which action considerably relleves the manufacturing requirements.

In miniature relays as referred to above, means are commonly adopted to prevent contacts which are made.

from being disengaged due to bounce, chatter or relative movement of the contacts when first coming into engagement. Examples of means for this purpose are disclosed in British patent specifications 484,472 and 673,867 and such means may clearly be applied without difiiculty to the present improved relay, and such damping means may be applied to the stationary contacts and may take various forms as will be indicated below.

In order that the invention may be more readily understood and carried into eifect, an example of a polarised electromagnetic relay constructed in accordance with the invention will now be more fully described with reference to the accompanying drawings, in which:

Figure l is a front elevation of the relay completely assembled;

Figure 2 is a plan of the same shown partly in section I the driving structure following that shown in those figures with relatively small modifications. Incidentally, the permanent magnets 1 are shown in accordance with British patent specification No. 715,630 in order that the two magnets may be exactly balanced. The framework 2 of the driving structure is, however, relatively shortened in such a way that the head or upper free end of the vibratory armature 3 projects some distance upwards beyond the other parts of the driving structure. The armature does not carry any moving contact, however, but has mounted in it two contact-actuating balls 4 of insulating These may be of mineral or ceramic material but it is preferred to make them of fused titanium dioxide (rutile). As can be seen from Figures 2 and 4, these balls project to a certain extent beyond the opposite faces of the 4 tapped holes, one on each of its opposite faces to receive a pair of screws 5 which pass through lugs 6 on the base plate 7 of the contact structure for fixing the latter in position with respect to the driving structure. It will be noted that as a result, the base plate 7 lies in a plane at right angles to the major extension of the pivoted armature 3, when the driving structure and the contact structure are secured together by the two screws 5. v

The contact structure as clearly seen in Figures 2 and 4 consists mainly of a number of insulating bars sandwiched together with the intervening contact members and all secured rigidly together by a pair of bolts 8 and nuts 9 and to the base plate 7 by screws 10 which pass through apertures 11 in the base plate 7 and are threaded into a retaining plate 12 immediately below the base plate 7. Both the base plate 7 and the retaining plate 12 have central apertures 13, 14 through which the upperend of the armature 3 passes freely. The apertures 11 in the base plate 7 are transverse slots as shown in Figure 4 so that merely by loosening the two screws 10, the whole contact structure can be moved laterally to alter the arrangement of the relay, for example, from centre-stable to one-sidestable as already indicated. Then the screws 10 are tightened to fix the contact structure in the adjusted position. When the contact structure is secured in position on the driving structure, the insulating balls 4 carried by the armature 3 just engage with the opposite moving contact members 15, 16 of the relay as clearly seen in Figure 2 so that as soon as the armature 3 begins to move, it immediately begins to displace either the moving contacts 15 or the contacts 16. a

The insulating bars of the contact structure are only of two kinds, namely a pair of outer bars or strips 17, 18 which extend across the whole width of the contact structure and a pair of central bars 19, 20 which extend from either side to less than half the total width. The moving contact members 15, 16 are thin metal strips bearing the moving contacts 21 and clamped by the securing bolts 8 between the central insulating bars 19, 20 and the outer bars 17, 18 on either side. All of these insulating bars are made from the same material such as a ceramic insulator and then may be finished within very fine limits of precision by grinding in thickness only. It should also be noted that there are only two kinds of contact members, the four inner movable members 15, 16 and the outer or static contact members 22 bearingthe static contacts 23. It will be seen from Figure 2 that the moving contact members 15, 16 extend towards the centre line beyond the central insulating bars 19, 20 but do not meet. The actuator balls 4 on the armature press the moving contacts 21 on one side or the other so as to bring them into contact with the corresponding pair of static contacts 23. Therefore, as illustrated, the relay is a double changeover relay and is centre-stable. Each of the securing bolts 8 passes through the two outer insulating bars 17, 18, one of the central insulating bars 19, 20 and to moving contact members 15, 16 and also at its ends, through two static contact members 22. Insulation is provided for by an insulating internal bush 24, best seen on the right of Figure 2 and surrounding each of the bolts 8. The static contactfmembers 22 at either side of the relay are electrically connected by the respective bolt 8 while the two moving contact members 15, 16 are completely insulated both from the bolt 8 and from the contact members 22. The bushes 24 are made of the same insulating material as the insulating bars 17, 18, 19 and 20.

Each of the central insulating bars 19, 20 is formed with a raised part 25, which parts are spaced apart sufiiciently to allow the armature 3 to pass freely between armature and they are situated so that their centres lie on I a line at rightangles to the longitudinal central plane of The driving structure further has two them. The parts 25 thus provide buffer surfaces to determine the back or retracted positions of the moving contact members 15; 16 which can be stressed against the parts 25 to any desired degree. This stressing can obviously be controlled-by bending the spring members towards or away from the butter members 25 before tightening the assembly bolts and nuts 8 and 9. The outer insulating bars 17, 18 also each has two raised parts 26 in such a position that the outer or static contact members 22 can be adjusted by screws 27 which are threaded in the members 22 and bear against the respective raised parts 26. Thus by means of the adjusting screws 27, each of' the static contacts 23 can be moved slightly inwards or outwards to provide the necessary precise adjustment of the gap between each moving contact 21 and the corresponding static contact 23 which may be up to the order of 0.005 inch. This gap is thus maintained constant when the screw 27 has been locked.

It will therefore be appreciated that the complete contact structure is a rigid self-contained unit attached by the bolts to the base plate 7 through which they pass and the bolts 10 at their lower ends are screwed into the retaining plate 12 and the base plate 7 is rigidly fixed to the driving structure by the bolts 8 passing through the lugs 6. By loosening the bolts 10 as already mentioned, the contact structure can be readily set to compensate for positional errors in the armature 3 with much greater case than has been possible hitherto. Furthermore, the relay can be set for one-side-stable working in, either sense by appropriate displacement of the contact structure in the appropriate direction and by adjustment ofthe armature bias.

The raised buffer parts 25 on the central insulation bars 19, are finished by grinding to a width exactly equal to the diameter of the two insulating balls 4 mounte'd inthe upper end of the armature 3. The use of a mineral or ceramic insulating material such as titanium dioxide for these balls has several advantages. One mechanical advantage is that it enables the distance between the contact points on opposite sides of each insulating ball 4 to be set to a value which is fixed and unchanged during the whole life of the relay. Electrically, a very high order of insulation resistance can be provided between the armature and the contact members and in fact, once the armature is effectively isolated by these means, the disposition and dimensions of the moving and static contacts are such that the same order of insulation resistance can readily be obtained for both. Furthermore, in the case of a centre-stable change-over relay as illustrated, the tensioning of the movable contact members 15, 16 against their buffer members places a corresponding stress on the insulating balls 4 and thus establishes two position-determining forces acting on either side of the armature 3. These, moreover, are fully controllable and make it possible for the forces to be exerted by the armature spring suspension to be reduced to the minimum values. Of course with the construction illustrated, the armature 3 has to exert a force to overcome the tension of the movable contact members 15, 16 against the buffer member 25 before any movement of the contact member 15, 16 takes place and this is very valuable in cases in which the relay is subject to impulse shocks, vibrations, the effect of interference currents or other disturbances.

It has already been mentioned that it is desirable to provide the static contacts with means for damping them and preventing chatter and that the form of construction described lends itself to the use of such means as are disclosed in British patent specifications 484,472 and 673,867 although such means are not shown in the drawings. It will be observed, however, that the static contacts 22 are shown in Figure 2 as cranked inwardly towards their inner ends. As a result of this when the movable contacts 21 encounter the static contacts 23, the latter are pressed backwards to a degree and relative 6 slidingi occurs between the cooperating contacts which sets up a measure of contact damping.

We claim:

1; A polarized electromagnetic relay comprising a complete driving structure including a framework and a contact structure complete in itself and detachably afiixed as a unit to the framework of said driving structure, said contact structure including a second framework, a yieldable support secured to said second framework, a moving contact mounted on said support, a static contact capable of being relatively adjusted independently of said driving structure, a fixed buffer member rigid with said second framework and located to serve as a backstop for said moving contact, means for stressing said moving contact against said fixed buifer member when the relay is not actuated and a vibratory armature which extends beyond the framework of said driving structure and which abuts against the yieldable support of said moving contact when said contact structure is in position afiixed to said driving structure so as to actuate said moving contact directly.

2. A polarized electromagnetic relay according to claim I, also comprising an actuator formed of electrical insulating material carried by said armature and in direct driving contact with the yieldable support of said moving contact.

3. A polarized electromagnetic relay according to claim 2, comprising two moving contacts having their yieldable supports respectively in contact with said actuator on opposite sides thereof when the relay is not actuated.

4. A polarized electromagnetic relay according to claim 2,- wherein said actuator consists of an accurately ground ball of electrical-insulating mineral material.

5. A polarized electromagnetic relay comprising a complete driving structure including a framework and a contact structure complete in itself and detachably aiiixed as a unit to the framework of said driving structure, said contact structure including a second framework, a yieldable support secured to said second framework, a moving contact mounted on said support, a static contact capable of being relatively adjusted independently of said driving structure, a fixed butter member rigid with said second framework and located to serve as a back-stop for said moving contact, means for stressing said moving contact against said fixed buffer member when the relay is not actuated, said contact structure comprising a contact spring-set for actuating circuits controlled by the relay, and said driving structure comprising a vibratory armature insulated from said spring contacts and not carrying any current.

6. A polarized electromagnetic relay comprising a complete driving structure including a framework and a contact structure complete in itself and detachably afiixed as a unit to the framework of said driving structure, said contact structure including a second framework, a yieldable support secured to said second framework, a moving contact mounted on said support, a static contact capable of being relatively adjusted independently of said driving structure, a fixed buffer member rigid with said second framework and located to serve as a back-stop for said moving contact, means for stressing said moving contact against said fixed butter member when the relay is not actuated and wherein said contact structure is mounted so as to be adjustable as a unit relatively to said driving structure in a direction generally the same as the direction of movement of said contacts during operation of the relay.

7. A polarized electromagnetic relay according to claim 5, wherein an insulating bar is sandwiched between the yieldable supports of said cooperating contacts to provide the insulation of said contacts.

8. A polarized electromagnetic relay comprising a fcornplete driving structure including a framework and a contact structure complete in itself and detachably afiixed as a unit to the framework of said:driving st'ructurefsaid contact structure including a second framework, a yieldable support secured to said second framework, a moving contact mounted on said support, a static contact capable of being relatively adjusted independently of said driving structure, a fixed buffer, member 'rigid with said second framework and located to serve as a back-stop for said moving contact, means for stressing said moving contact against said fixed buffer member when the relay is not actuated and said moving and static contacts are separated by a flat insulating member finished by thickness grinding only.

9. A polarized electromagnetic relay comprising a complete driving structure including a framework and a contact structure complete in itself and detachably atfixed as a unit tocthe framework of said driving structure, said contact structure including a second framework, a yieldable support secured to said second framework, a moving contact mounted on said support, a static contact capable of being relatively adjusted independently of said driving structure, a fixed buffer member rigid with said second framework and located to serve as a back-stop for said moving contact, means for stressing said moving contact against said fixed buifer member when the relay is not actuated and the supports of said moving contact and said static contact are formed of the same electrically-conductive material and the insulating parts of said contact structure are all formed of the same electrically-insulating material.

10. A polarized electromagnetic relay comprising a complete electromagnetic driving structure including a framework and a contact structure complete in itself and detachably afiixed as a unit to the framework of said driving structure, said contact structure including a'secend-framework, a yieldable support securedto said second-framework,;a moving contact mounted on said support, a static contact, means for adjustablypositioning said static contact independently ofsaid driving structure, a rigid buffer of insulating material fixed on said second framework and located to serve as a back-stop for said'moving contact, and means for stressing said moving contact against said fixed buffer member when the relay is not actuated.

11. A polarized electromagnetic relay according to 1 claim '10, wherein the contacts are set in said contact 15 structure with said moving contact and said static contact having a gap therebetween not greater than 0.005 inch.

References Cited in the file of this patent UNITED STATES PATENTS 145,253 Australia Feb. 19, 1952

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